The neural retina processes visual information and relays it to the brain. It provides an excellent system for many of our studies for several reasons:1) the visual system undergoes complex developmental patterning as well as clinically significant age-associated decline; 2) much is known about retinal circuit formation; and 3) retinal neurons themselves are accessible to study in vivo.
There are five general neuron types in the retina. Photoreceptors detect visual stimuli. Interneurons (horizontal, bipolar and amacrine cells), process these signals, and retinal ganglion cells (RGCs) integrate this information and send it to the brain. Retinal neurons can be further subdivided into ~70 distinct functional subtypes. While this number of subtypes is comparable to that of other brain regions, markers for a majority these cells have been well defined only in retina. Moreover, specific types of retinal neurons pattern and connect in precise nuclear and synaptic layers.
Because the circuitry of the retina is well understood, molecular, cellular and functional studies can be completed in parallel and readily interpreted. This is more challenging in the brain where cells and synapses of many types are closely intermingled.